1. Field of the Invention
The present invention relates to circuits that protect against overvoltages, which circuits can be used in particular for subscriber line interface circuits (SLIC).
2. Discussion of the Related Art
Telephone circuits connected to lines are particularly likely to be disturbed by overvoltages such as lightning discharges or accidental connections to lines of the electric power network. Further, the problem of the protection of interface circuits becomes more and more acute as these interface circuits are formed of more and more integrated circuits of smaller and smaller dimensions and accordingly, more and more sensitive to overvoltages.
The applicant has been studying SLIC protection circuits for many years and has already devised several novel circuits, monolithically implementable, which are described, in particular, in U.S. Pat. Nos. 5,274,524, 5,243,488, 5,696,391 and 5,684,322, and in European patent applications 0742592 and 0687051.